Networking and Data Communications Library Introduction to Tandem X.25 Capabilities Product Version C30.08/D10 Release ID C30.08/D10 Edition Print Date Part Number Abstract September 1992 065307 This manual reviews X.25 concepts and provides basic information about Tandem X.25 products.
Document History Edition Part Number Product Version Release ID Print Date First 065307 C30.08/D10 C30.08/D10 September 1992 New editions incorporate any updates issued since the previous edition. Release ID Note Release ID specifies the release in which the software functions described in an edition are first available on a standard SUT (site update tape). Copyright Copyright © 1992 by Tandem Computers Incorporated. All rights reserved.
Contents Preface Section 1 ix What is X.25? Multi-Vendor International Communications Protocol Benefits of X.25 1-1 Need for a Common Standard 1-1 Comparing X.25 with other Networking Standards Using X.25 for Direct Connections 1-5 PAD-Related Standards PAD 1-6 1-4 1-6 Internetwork Related Standards 1-9 Addressing in X.25 Networks 1-10 Port Numbers or Subaddressing X.
Contents Section 2 Tandem X.
Contents Appendix A Networks Supported by X25AM Appendix B X25AM Parameters Appendix C Utilities for Managing X25AM Distributed Systems Management C-1 Subsystem Programmatic Interface (SPI) C-1 Subsystem Control Facility (SCF) C-1 Viewpoint Console Application C-1 Event Management Service (EMS) C-2 NonStop NET/MASTER Management Services Peripheral Utility Program (PUP) C-2 C-2 Dynamic System Configuration (DSC) C-2 Tandem Maintenance and Diagnostic Subsystem (TMDS) Measure Appendix D C-2 C-3
Contents Figures vi Figure 1-1. Proprietary Networking Conventions Figure 1-2. X.25 Connection Figure 1-3. Comparison of X.25, OSI, and SNA 1-5 Figure 1-4. Placement and Functions of a PAD 1-7 Figure 1-5. PAD-Related Standards Figure 1-6. Standards for Connecting Networks Figure 1-7. X.121 Address Format Figure 1-8. X.25 Layers Figure 1-9. Packaging Data for Transmission Figure 1-10. Logical Channel Assignments Figure 1-11. Packet Header Structure Figure 1-12.
Contents Figure 2-12. Switched Primary SNAX/XF Station over X25AM Figure 2-13. Switched Secondary SNAX/XF Station over X25AM Figure 2-14. Calling Out to Remote IBM Intelligent Terminals Figure 2-15. Calling Out from a Tandem System to an IBM System Figure 2-16. Enabling Call In Figure 2-17. Calling In or Calling Out through Multiple SNAX/CM Processes 2-29 Figure 2-18. WAN/LAN Connectivity Figure 2-19. Connecting Tandem Systems to an OSI Network Figure 3-1.
Contents viii 065307 Tandem Computers Incorporated
Preface About This Manual The Introduction to Tandem X.25 Capabilities provides basic information about Tandem X.25 products. This manual includes: A review of X.25 concepts An overview of the X25AM subsystem Information about other Tandem products that can be used with X25AM for different types of connectivity Information about Tandem management and configuration products that can be used with X25AM This manual, along with the X25AM Programming Manual, replaces the X25AM Manual.
Preface Related Reading The Introduction to Tandem X.25 Capabilities is part of the X25AM manual set. The following table summarizes the current X25AM manual set and provides a synopsis of each document. Title of Manual Synopsis Introduction to Tandem X.25 Capabilities SCF Reference Manual for X25AM System Generation Manual for X25AM X25AM Programming Manual Provides an overview of the X.25 standard and the Tandem implementation using X25AM.
Preface Introduction to Tandem X.25 Capabilities Introduction to Tandem Networking and Data Comm Introduction to Distributed Systems Mgmt (DSM) Subsystem Control Facility (SCF) Reference Manual X25AM Programming Manual SCF Reference Manual for X25AM X25AM Management Programming Manual System Generation Manual for X25AM 000 Your Comments Invited After you have had a chance to use this manual, please take a moment to fill out the Reader Comment Card at the back and send it to us.
1 What is X.25? This section provides an overview of X.25 concepts and related standards. If you are already familiar with X.25 concepts and terminology, you may want to skip this section. Multi-Vendor International Communications Protocol Benefits of X.25 One of the most common ways to connect computer systems that are in remote locations —rather than in a single building or campus — is through a packet-switching data network (PSDN). The protocol used for connecting computer systems to a PSDN is X.25.
What is X.25? Multi-Vendor International Standard Figure 1-1. Proprietary Networking Conventions Tandem System Tandem System Expand Expand Tandem System Expand IBM System IBM System SNA SNA IBM System SNA 001 Recognizing the need for a standard, the CCITT (International Telegraph and Telephone Consultative Committee) developed the X.25 recommendation as an international data communications standard specifying how to connect user computer systems to public data networks.
What is X.25? Multi-Vendor International Standard as an international standard of data communications. It is customary for networks and computer manufacturers to indicate which year(s) of the X.25 recommendation they support. Tandem supports the 1980 and 1984 standards. The X.25 standard was developed primarily for public networks, but it is also used for connecting computer systems to private packet-switching data networks.
What is X.25? Comparing X.25 with other Networking Standards is an asynchronous terminal, it must be equipped with an additional hardware or software interface that is capable of sending and receiving packets. The DCE can be a modem, a piece of cable, or a network processor. Note that when two host computers are connected through a PSDN, the connection involves two DTE/DCE interfaces. Comparing X.25 with X.
What is X.25? Comparing X.25 with other Networking Standards Figure 1-3. Comparison of X.25, OSI, and SNA OSI SNA Layers Application Transaction Services 7 Presentation Presentation Services 6 Session Data Flow Control 5 Transport Transmission Control 4 Packet (Network) Network Path Control Link (Frame) Datalink Datalink Control Physical Physical Physical Control X.25 3 2 1 003 Using X.25 for Direct Connections Although X.
What is X.25? PAD-Related Standards PAD-Related Many CCITT standards are associated with X.25, because they concern the way that Standards different types of user equipment connect to each other and to the network. Like X.25, these standards (described below) are meant to ensure interoperability between the various computers and devices that communicate with a PSDN. PAD A Packet Assembler/Disassembler (PAD) is a device that allows an asynchronous terminal or personal computer to access a PSDN.
What is X.25? PAD-Related Standards Figure 1-4. Placement and Functions of a PAD PAD A B PSDN C Characters X.3 Packets PAD A B C Characters X.
What is X.25? PAD-Related Standards X.28 X.28 defines how an asynchronous device communicates with a PAD in a public data network in the same country (see Figure 1-5). X.29 X.29 defines the procedures that an X.25 DTE must follow to control the operation of a PAD during communications with an asynchronous DTE through the PAD (see Figure 1-5). Figure 1-5. PAD-Related Standards X.29 X.25 DTE X.28 PAD PSDN X.3 X.28 PAD X.
What is X.25? Internetwork-Related Standards Internetwork-Related The interfaces that connect one network to another are also regulated by CCITT Standards standards, as described below. X.75 The X.75 standard defines the procedures that must be followed to connect public packet-switching data networks through a gateway interface. The X.75 standard applies to international circuits; however, it does not apply to the connection of private networks (see Figure 1-6).
What is X.25? Addressing in X.25 Networks Addressing in X.25 Every subscriber to a network must have a unique address. An international Networks numbering plan, specified by CCITT standard X.121, dictates the format of each address. This standard originally applied to public data networks, but is now used also for connections to private networks. Every connection is allocated an address which can contain up to 15 digits (Figure 1-7). Figure 1-7. X.
What is X.25? X.25 Layers reach individual employees by dialing directly to the telephone number of an individual office.) The actual number of subaddresses supported depends upon the particular network and computer system. X.25 Layers The X.25 standard provides rules for communicating on the first three functional layers of a data communications model (see Figure 1-8).
What is X.25? Packet-Layer Components Figure 1-8. X.25 Layers DTE User Defined Processes Layers 4 - 7 X.25 Packet (Network) X.25 Link (Frame) X.25 Physical DCE Peer Protocols Packets Frames Electric Signals 008 Packet-Layer The Packet Layer (layer 3), as its name implies, is really the essence of communicating Components in an X.25 packet-switching environment. Data from a user system is packaged into packets for transmission through a packet-switching network to a specified destination.
What is X.25? Packet-Layer Components Figure 1-9 . Packaging Data for Transmission Source DTE Upper Layers Destination DTE Data Upper Layers Data Packet Layer Packet Layer Packet Packet Frame Layer Frame Frame Layer Frame Electric Signals Physical Layer Electric Signals Physical Layer 009 Routing The Packet Layer provides two types of virtual circuits for the routing of information from one location to another: switched virtual circuits (SVCs) and permanent virtual circuits (PVCs).
What is X.25? Packet-Layer Components Permanent Virtual Circuit (PVC) — A permanent virtual circuit provides a permanent logical channel assigned exclusively to the calling DTE. A PVC automatically connects a DTE to a predetermined destination. Devices do not need permission to transmit to each other. No control packets are required to establish or end the call. A PVC is analogous to a private or leased point-to-point line.
What is X.25? Packet-Layer Components Figure 1-10. Logical Channel Assignments Logical Channel Numbers LCN Restart/Diagnostic/ Registration 0 Reserved 1 Permanent Virtual Circuit N One-Way Incoming Virtual Circuit DCE Only incoming calls from the network N Two-Way Virtual Circuit For shared use by DTE and DCE during peak traffic flow.
What is X.25? Packet-Layer Components Figure 1-11. Packet Header Structure Bit Octet 1 Octet 2 8 7 6 5 General Format Identifier 4 3 2 1 Logical Channel Group Number Logical Channel Number Octet 3 Packet Type Identifier Octet 4 Either User Data or Additional Control Fields 011 Packet Header The packet header contains the following peer-to-peer protocol information: General Format Identifier (GFI) — Indicates the general format of the rest of the header.
What is X.25? Packet-Layer Components Packet Type Identifier (PTI) — Indicates the specific packet type being transmitted. There are five general types of packets, which are described in the next subsection. M bit — Indicates that more user data is coming in some following packets. When the packet is carrying user data, the third octet of the packet header can contain an M bit. The M bit identifies a sequence of related packets passing through the network.
What is X.25? Packet-Layer Components Figure 1-12. CUD in Call Setup Packets Bits Octet 1 8 7 6 5 0 D S N 4 3 2 Logical 2 Channel Identifier 3 Packet Type Identifier (PTI) 4 Calling DTE 1 Called DTE DTE Addresses 0 0 Facility Length Facility Fields Call User Data 1–16 Octets (in Call Request and Incoming Call Packets only) Legend 0 = The initial bit (Q bit) is set to zero in call-setup packets. D = The delivery bit (D bit).
What is X.25? Packet Types Packet Types X.25 defines five general types of packets, which perform different packet-level communications functions. Call-Setup and Clearing Data and Interrupt Flow Control and Reset Restart Diagnostic Each of these general packet types includes one or more specific packet types. Call Setup Packets Call setup packets are required to establish a switched virtual circuit. Call setup packets are not used by permanent virtual circuits.
What is X.25? Packet Types Call Clear Packets Call clear packets are used to clear a DTE-to-DTE session on a switched virtual circuit. Call clear packets are not used by permanent virtual circuits. Call clear packets contain all the information included in the call-setup packets, plus the clearing cause field (mandatory) and the diagnostic code (optional).
What is X.25? Packet Types Data Packets Data packets contain user data. During the data transfer stage, both DTEs can exchange data. If a DTE does not have any data to send, it replies with an RR packet (see Figure 1-15). The RR packet acknowledges the packets received thus far and indicates the readiness of the DTE to receive additional packets. Figure 1-15.
What is X.25? Packet Types Figure 1-16.
What is X.25? Packet Types Interrupt Packets Flow-Control Packets A DTE can transmit one nonsequenced interrupt packet without following normal flow-control procedures. This type of packet is used for unusual conditions, such as a high-priority message. Once an Interrupt packet is sent, the sender cannot transmit a second Interrupt packet until the first one is acknowledged by an Interrupt Confirmation packet.
What is X.25? Data-Link-Layer Components Data-Link-Layer The Data Link Layer (layer 2) includes the procedures and data frame formats used to Components establish the data-link-layer connection between the DTE and the DCE. The Data Link Layer must set up the link, initiate the communication, and handle error-recovery. At the originating or source location, the Data Link Layer receives packets from the Packet Layer. It appends frame-header information to this packet to create a frame.
What is X.25? Data-Link-Layer Components Figure 1-17.
What is X.25? Data-Link-Layer Components Frame Structure Data is exchanged between the two stations in frames. The X.25 frame structure is based on the HDLC frame format (Figure 1-18). Figure 1-18. X25 Frame Format Packet Level Frame Level Packet Flag Address Control Information FCS Flag 014 Frames contain the following fields: 1–26 Flag The start of a frame is always indicated by a flag, which is a sequence of 8 bits (01111110), six ones preceded and followed by a zero.
What is X.25? Data-Link-Layer Components For S-frames and U-frames, the control field contains the command or response. Other components of the control field are: N(S) — Number Sent Variable or Send Sequence Number is only included in the control field of I-frames. It identifies the sequence of the current I-frame, so that the other end can check to make sure that it has received all preceding I-frames. N(R) — Number Received Variable or Receive Sequence Number is included in both I-frames and S-frames.
What is X.25? Data-Link-Layer Components Figure 1-19 shows the location of the address field within the frame format, and indicates the how the frame address identifies the frame as a command or response. Figure 1-19.
What is X.25? Data-Link-Layer Components Figure 1-20 illustrates the data transfer portion of a communications session between a DTE and a DCE. Keep in mind that only information frames (I-frames) can contain packets. Figure 1-20.
What is X.25? Data-Link-Layer Components Frame-Layer Modulos and Window Size Information frames (I-frames) contain sequencing numbers for I-frames sent and I-frames received: N(S) identifies the sequence number of the I-frame sent. N(R) identifies the sequence number of the I-frame that is expected to be received The sequencing numbers make it possible to ensure that all the I-frames that are sent are received by the other end.
What is X.25? Frame Types Frame Types The X.25 standard defines three basic frame types, which perform different communications functions. Information frames (I-frames) Supervisory frames (S-frames) Unnumbered frames (U-frames) I-Frames S-Frames I-frames transport information from the originating or source computer system to the destination system. The information (the packet received from layer 3) is carried within the I-field of an I-frame.
What is X.25? Frame Types Figure 1-21 shows how REJ frames are used for error recovery. When the DTE attempts to send its third transmission of an I-frame, the DCE responds with REJ and N(R) of 1. This sequence number notifies the DTE that the DCE has successfully received only one I-frame, S0. Thus, the DTE resends I-frames, starting with S1. Figure 1-21.
What is X.25? Frame Types U-Frames Unnumbered frames are used primarily to establish and disconnect the link . The U-frames used by LAPB are: SABM — Set asynchronous balanced mode (SABM). A SABM command is sent to establish the link. In asynchronous balanced mode communications, either station can establish the link. UA — Unnumbered acknowledgement (UA). A UA is sent in response to a SABM, indicating that the other end has received the SABM and is ready to accept further communications.
What is X.25? Frame Types In Figure 1-22, the DCE returns an RR response with an N(R) of 4. However, the DTE had only sent I-frames up to an N(S) of 2 and would therefore expect an N(R) of 3 in response for acknowledgement. To recover from this situation, the DTE sends the FRMR command with appropriate diagnostic information. Then, the DCE responds with a SABM to reset the link. Figure 1-22.
What is X.25? Physical-Layer Components FRMR-Frame Diagnostic Field The diagnostic field of the FRMR indicates an error condition such as: Receipt of a control field that is invalid. Receipt of an information field that exceeds the maximum established length. Receipt of an invalid N(R) number from the remote station.
What is X.25? Physical-Layer Components RS-232-C / RS-232-D Tandem RS-232-C is limited to data signalling rates of 20 kbps and a cable distance of 50 feet between the DTE and the DCE. (RS-232-D includes the specification of the DB-25 connector used with RS-232-C.) RS-232-C is similar to CCITT’s V.24/V.28 interface and electrical characteristic recommendations used in Europe. RS-449-1/ RS-422 and RS-423 RS-449-1 was intended to replace RS-232-C; however, it was not commonly used until recently.
2 Tandem X.25 Features and Capabilities This section describes the features and capabilities provided by the X.25 Access Method (X25AM), the Tandem product for X.25 connectivity. If you are not already familiar with X.25 concepts and terminology, please refer to Section One, “What is X.25?” X25AM Scope of Support X25AM connects Tandem computer systems to public and private data networks using the X.25 standard set of networking conventions.
Tandem X.25 Features and Capabilities X25AM X25AM line — The X25AM line is a physical entity attached to a Tandem controller, which is capable of supporting X.25 communications. The X25AM line is configured as a device by the system generation program (SYSGEN). While configuring a line, you can specify basic line characteristics (subscription parameters): timers, retries, frame size, default window size, default packet size, default throughput class, and extended packet sequencing capability.
Tandem X.25 Features and Capabilities X25AM Figure 2-1 illustrates the physical and logical components of the X25AM subsystem. Figure 2-1. X25AM Subsystem Components Tandem System Application Process X25AM I/O Process X25AM Lines Application Process • • • Application Process • • • Application Process (X25AM Subdevices) Circuits X.
Tandem X.25 Features and Capabilities Flexible Call-Setup Flexible Call-Setup X25AM provides flexible call setup options to meet your application needs through a combination of permanent and switched virtual circuits, subaddressing, and optional user facilities. Permanent and Switched Virtual Circuits Up to 254 circuits can be configured for each X25AM line. (For D-series systems, up to 511 circuits can be configured.
Tandem X.25 Features and Capabilities Flexible Call-Setup Figure 2-2. Subaddressing PORT # 1 Subdevice A Subdevice B DTE 3110123456789 DTE Address: 3110123456789 Port Number: 1 Called Address: 31101234567891 DTE Address: 3110123456789 Port Number: 2 Called Address: 31101234567892 PORT # 2 Subdevice C 020 Optional User Facilities Optional user facilities are also referred to as per-call facilities: they can be exercised or not exercised on a per-call basis.
Tandem X.
Tandem X.25 Features and Capabilities Flexible Call-Setup Reverse Charging Request and Acceptance These facilities allow the destination DTE to accept the packet network charges (like a collect call on a telephone network). The reverse charging request and acceptance facilities can be used with either virtual calls or fast selects. Although these facilities are closely related, they do not necessarily have to be used together. Reverse charging requests the remote DTE to pay for the call.
Tandem X.25 Features and Capabilities Flexible Call-Setup Negotiation of Window Size This facility allows the user to negotiate an appropriate window size during call setup. X25AM accepts any Incoming Call packet that requests window-size negotiation. However, window-size negotiation is included in a Call Accepted packet only when the subdevice issuing the response is configured to negotiate window size (NEGOTIATE attribute).
Tandem X.25 Features and Capabilities Flexible Call-Setup Call Redirection with Notification The call redirection facility redirects calls when the destination DTE is busy, is out-of-order, or has requested a call redirection. This facility allows a call to be rerouted to a backup DTE, so that problems and failures do not affect the end user. Call redirection can also permit calls to be redirected to different parts of a country to allow for time-zone differences.
Tandem X.25 Features and Capabilities Flexible Call-Setup Transit Delay Selection and Indication This facility permits a DTE to select a transit delay time through the packet network. This feature is used mostly for long distance connections through a network. The transit delay is established on a per-call basis, and the appropriate delay value is supplied by the network at subscription time.
Tandem X.25 Features and Capabilities Flexible Call-Setup gateways. If the RPOA selection facility is used, the call-request packet contains a list of specific RPOAs, which have been selected to handle that call. The RPOA attribute can be specified for either a line or a subdevice. If both the line and subdevice attribute are specified, the subdevice attribute is used. The user application can also specify a dynamic value for a subdevice.
Tandem X.25 Features and Capabilities X25AM Connectivity REMOTENET attribute, X25AM applies the same set of networking characteristics to both incoming and outgoing calls. X25AM Connectivity X25AM can be used by itself or with other Tandem products to provide connectivity for a variety of network configurations that use Tandem systems to access PSDNs. The type of connectivity you require determines whether or not you will need to write a user application for X25AM or for a higher-level Tandem product.
Tandem X.25 Features and Capabilities X25AM Connectivity Figure 2-4. User Application and X25AM Connectivity Your Applications TACL Pathway/ Expand SNAX/ TCP/IP OSI/AS TCP XF SysWay OSI/TS X3PAD Other Tandem Processes X25AM I/O Process Bit-synchronous Controller or General-purpose Controller Controllers X.
Tandem X.25 Features and Capabilities X25AM Connectivity messages issued from the network. X3PAD can also transfer data from Guardian files to the network, or from the network to Guardian files. The X3PAD program is based on CCITT Recommendation X.3, which describes the functions of a PAD and the parameters associated with the asynchronous terminals accessing the PAD. X3PAD also supports the procedures of Recommendation X.
Tandem X.25 Features and Capabilities X25AM Connectivity Connecting Remote Asynchronous Terminals To connect a Tandem system to a remote terminal through a PSDN, you define the terminal as an X25AM Interactive Terminal Interface (ITI) subdevice. The ITI protocol allows users at remote locations to communicate with an application process as though the terminal were connected directly to the computer system through an asynchronous controller.
Tandem X.25 Features and Capabilities X25AM Connectivity Application Process Controlling a Remote Terminal An application process controls the end-to-end interface between the remote terminal and the Tandem system. The application uses standard Guardian file-system procedure calls. The application does not have direct access to the packets, but it can obtain and modify some packet fields through the procedure calls.
Tandem X.25 Features and Capabilities X25AM Connectivity Connecting to a PAD without a PSDN You can also use X25AM to connect a Tandem system to multiple terminals over a single X25AM line by connecting the X25AM line to a PAD (Figure 2-7), and by defining the terminals as ITI subdevices. The PAD acts as a sort of multiplexer, connecting a single X25AM line to multiple asynchronous terminals or PCs.
Tandem X.25 Features and Capabilities X25AM Connectivity Connecting to a LAN through UB Access/One You can use X25AM to connect a Tandem system to a local LAN through an Ungermann Bass (UB) gateway (Figure 2-8). The LAN can consist of different types of terminals and printers. The various terminals and printers can all communicate through the UB Access/One interface to a Tandem system over a single X25AM line.
Tandem X.25 Features and Capabilities X25AM Connectivity Connecting to other Hosts via PSDNs To connect a Tandem system to a computer system of other vendor via a PSDN, you define an X25AM subdevice for the PTP (process-to-process) protocol. Figure 2-9 shows a Tandem system connected to another manufacturer’s computer system over a PSDN. In this type of configuration, a user application must be written to the X25AM process.
Tandem X.25 Features and Capabilities X25AM Connectivity Connecting Multiple Tandem Systems Tandem systems are usually connected to each other by using the Expand product. Tandem systems at remote locations can communicate with each other via a PSDN by using the Expand process over an X25AM line. Like other X.25 connections, the cost of data communications may be less than it is for dedicated lines when line use is intermittent. The Expand subsystem’s implementation of X.
Tandem X.25 Features and Capabilities X25AM Connectivity Figure 2-10 shows the connection of two Tandem systems over a packet-switched data network using the X25AM NAM protocol. Figure 2-10. Connecting Multiple Tandem Systems through a PSDN Boston Cupertino Tandem NonStop System Tandem NonStop System Expand Expand X.25 Packet-Switched Network X.
Tandem X.25 Features and Capabilities X25AM Connectivity Connecting to InfoWay via SysWay Many customers use the SysWay communications product over X25AM to access the InfoWay service, which provides electronic access to the Tandem account team and to Tandem product information. InfoWay resides on a Tandem corporate system.
Tandem X.25 Features and Capabilities X25AM Connectivity Connecting to SNA Networks To connect a Tandem system to an SNA network via a PSDN, you define the X25AM subdevice for the Qualified Logical Link Control (QLLC) protocol . You must also use the SNAX/XF product. The SNAX/XF process runs over the the X25AM line.
Tandem X.25 Features and Capabilities X25AM Connectivity A Tandem SNAX/XF secondary station functions as a type 2 node communicating with an IBM SNA host. See Figure 2-13. In this type of configuration, the Tandem system acts as a gateway between an application or device in the Tandem network and an application on the IBM host.
Tandem X.25 Features and Capabilities X25AM Connectivity SNAX/CM SNAX Connection Manager (SNAX/CM) extends the support provided by SNAX/XF, making it possible for the Tandem system to establish a call out to the remote SNA devices over an X25AM line. SNAX/CM supports only SVCs; it does not support PVCs. Using SNAX/CM, you can issue commands either from a terminal or an application. Typically, you would use an application to send either a call-request packet or a call-disconnect packet.
Tandem X.25 Features and Capabilities X25AM Connectivity Calling Out Figure 2-14 shows how a Tandem system can use SNAX/CM to programmatically call out to remote locations. For example, a retail business could schedule a program to summarize sales for each day, and the program would run each night after the stores closed . The Tandem system at the main office calls out to devices at remote locations to retrieve sales data from intelligent terminals.
Tandem X.25 Features and Capabilities X25AM Connectivity Calling Out from a Tandem System to an IBM System Figure 2-15 shows how a Tandem system can use SNAX/CM to initiate a call to an IBM host system over X.25 lines. Figure 2-15. Calling Out from a Tandem System to an IBM System Tandem NonStop System SNAX/CM Server X.
Tandem X.25 Features and Capabilities X25AM Connectivity Calling In to a Tandem System from an IBM System You can also use SNAX/CM to enable a centralized IBM host computer to establish a call to a Tandem system over an X.25 line. See Figure 2-16. Figure 2-16. Enabling Call In Tandem NonStop System SNAX/CM Server Tandem Application SNAX/XF QLLC X25AM X.25 IBM System IBM Application PSDN 033 In this example, a Tandem computer sends the receipts for the day to a centralized IBM host for processing.
Tandem X.25 Features and Capabilities X25AM Connectivity Calling In and/or Calling Out through Multiple SNAX/CM processes Multiple SNAX/CM processes can be used to support more complex configurations. See Figure 2-17. Figure 2-17.
Tandem X.25 Features and Capabilities X25AM Connectivity Connecting to LANs through TCP/IP A local area network (LAN) generally connects computer systems, workstations, or devices within a limited geographical area, such as within a building or a group of buildings. The Transmission Control Protocol/Internet Protocol (TCP/IP) is a de facto standard protocol used for multi-vendor LAN communications.
Tandem X.25 Features and Capabilities X25AM Connectivity Figure 2-18. WAN/LAN Connectivity Your Applications Simple Mail Transfer Protocol (SMTP) gateway Pathway Terminal Control Process Trivial File Transfer Protocol (TFTP) TELNET File Transfer Protocol (FTP) or TCP/IP Domain Name Service Sockets Interface UDP TLAM X25AM 802.
Tandem X.25 Features and Capabilities X25AM Connectivity Connecting to OSI Networks 2–32 X25AM provides the lower-layer data communications functions for Tandem OSI products. To connect a Tandem system to an OSI application, OSI/TS and OSI/AS configure an X25AM subdevice for the PTP (process-to-process) protocol. (For additional information on upper-layer OSI products, refer to the Tandem OSI/TS Manual, or Tandem OSI/AS Configuration and Management Manual.
Tandem X.25 Features and Capabilities X25AM Connectivity Figure 2-19. Connecting Tandem Systems to an OSI Network MHS Layer 7 FTAM FTAM Your Applications Layers 5,6,7 OSI/AS Layer 4 Other Tandem Processes Layers 2,3 OSI/TS (CLNP) IEEE 802.2 LLC 1 Interface I/O Processes X25AM TLAM IEEE 802.3 Ethernet/802.3 LAN Controller Bit 3650/6100 Synchronous or Communications Controller Family Controller To 802.
Tandem X.25 Features and Capabilities Tandem Hardware Environment Tandem Hardware X25AM lines can be configured on any of the controllers listed in Table 2-2. Environment Table 2-2.
3 X25AM Implementations This section describes some implementations of X25AM that have been used or are being used by Tandem customers. Each implementation description includes an illustration of the network configuration. Electronic Mail Messaging Using X.400 over X25AM The world’s largest value-added network connects to over 100 public data networks, and offers users a wide variety of dial-up and dedicated-access services based on Tandem X25AM.
X25AM Implementations E-Mail Messaging Using X.400 over X25AM Figure 3-1 illustrates how a large European retail organization is using Tandem systems and the services provided by this value-added network. The retailer first established a chain of grocery stores, and then expanded into banking, travel, insurance, oil, music stores, bookstores, restaurants, and hotels. The retail business currently includes 527 stores, 101 stores-on-wheels, and 191 restaurants.
X25AM Implementations E-Mail Messaging Using X.400 over X25AM Figure 3-1. Electronic Mail Messaging Using X.
X25AM Implementations Banking Application Using SNAX/XF over X25AM Banking Application An international bank has a variety of host computers located throughout the world, Using SNAX/XF over connected via a private X.25 network. Commercial customers can call at any given X25AM time to determine their combined financial position around the world. Before this service was automated, it used to take several days to compile the information.
X25AM Implementations Banking Application Using SNAX/XF over X25AM Figure 3-2. Banking Application Using SNAX/XF over X25AM Baltimore Branch NYC Branch Tandem System Customized Banking Application Tandem System Customized Banking Application Expand ••• X.25 SNAX/APC Commercial Customers SNAX/XF X25AM using QLLC protocol SQL Database X.25 Private Packet-Switching Network X.25 X.25 IBM Host IBM Host SNA London Branch X.
X25AM Implementations Using Identical X.121 Addresses for Load-Sharing Using Identical X.121 A bank in Europe has installed a private packet-switching network to provide Addresses for Ease of connectivity to its branch network of approximately 360 controllers, each connected to Load-Sharing about 8 workstations via a LAN (Figure 3-3). The banking application resides on a 4-processor Cyclone system, which is connected to the bank’s packet-switching network via 12 X25AM lines.
X25AM Implementations Using Identical X.121 Addresses for Load-Sharing Figure 3-3. Using Identical X.121 Addresses for Ease of Load-Sharing Branch Controllers Workstations 1 SVC LAN Multiplexer 12 X25AM Processes X.25 1 SVC ••• LAN 12 X25AM Lines Sharing the Same X.
X25AM Implementations Stock Exchange Using SNAX/XF and OSI over X25AM Stock Exchange Using A large stock exchange in Europe uses Tandem systems and X25AM for an online SNAX/XF and OSI over trading and information system that gives brokers quick and efficient access to a X25AM growing securities market. The Tandem system automatically matches buy and sell orders whenever price, volume, and other conditions are met.
X25AM Implementations Stock Exchange Using SNAX/XF and OSI over X25AM Figure 3-4.
X25AM Implementations Pharmacy Network Using X25AM ITI Pharmacy Network A large health care provider has installed a private packet-switching network to Using X25AM ITI connect its pharmacies (Figure 3-5). The network will eventually support over 100 Protocol pharmacies, both inpatient and outpatient. Each pharmacy has a terminal (a CRT and a cash drawer) connected to Tandem NonStop System via a PAD and a PSDN.
X25AM Implementations Pharmacy Network Using X25AM ITI Figure 3-5.
X25AM Implementations Using TCP/IP and OSI over X25AM Railway Reservation A railway reservation system combines LAN and WAN functions, by running TCP/IP System Using TCP/IP and OSI applications over X25AM (Figure 3-6). Transactions are initiated at terminals and OSI over X25AM connected to UNIX workstations over either an Ethernet LAN or a public data network.
X25AM Implementations Using TCP/IP and OSI over X25AM Figure 3-6 Railway Reservation System over both LAN and WAN Configurations NonStop System NonStop SQL SQL Database Pathway Servers Seat Reservation Database Pathway Servers Pathway Requesters Ethernet LAN IDS Pathway Requesters IDS Front Front End End Process Process Front End Process OSI/TS OSI/TS OSI/TS OSI/TS TLAM TLAM X25AM X25AM Ethernet LAN Front End Process Public Packet-Switching Data Network Nationwide Network of LANs Ethe
X25AM Implementations Interfacing with a Private Frame-Relay Network Interfacing with a Private Frame-Relay Network A large transportation company based in the United States has installed a reservations system on a Tandem Cyclone/R system, interfacing with a private frame-relay network. Frame-relay is a relatively new protocol providing faster, more efficient capabilities for packet-switching data communications.
X25AM Implementations Interfacing with a Private Frame-Relay Network Figure 3-7. Interfacing with a Private Frame-Relay Network Tandem Cyclone/R Application Pathway X25AM PC6530 12 X25AM lines ••• PAD PAD Frame Relay Router Frame Relay Router Frame Relay Router PC6530 PAD PC6530 Frame Relay Router PAD PC6530 052 .
Appendix A Networks Supported by X25AM This appendix provides a list of PSDNs currently supported by X25AM. The networks are listed alphabetically by country. Table A-1.
Networks Supported by X25AM Table A-1. X25AM-Supported PSDNs (Page 2 of 2) Country Service Spain Sweden Switzerland Taiwan United Kingdom United States IBERPAC Data Pac TelePak PacNet PSS Accunet Sprint (Telenet) Tymnet Westpac CSC Infonet BX.
Appendix B X25AM Parameters This appendix provides a summary of X25AM parameters. Tables B-1 through B-4 list the X.25 standard characteristics and provide a summary of the Tandem X25AM implementation of these characteristics. The tables include the X25AM range of values, default values, SCF attributes, and SYSGEN modifiers for specifying these characteristics. For a complete list of SCF attributes for X25AM, refer to the SCF Reference Manual for X25AM.
X25AM Parameters Table B-2 lists the X25AM parameters for packet-level characteristics. Table B-2.
X25AM Parameters Table B-2.
X25AM Parameters Table B-3 lists the X25AM parameters for switched and permanent virtual circuits and logical channel assignments. Table B-3.
X25AM Parameters Table B-4 lists the X25AM parameters for optional user facilities. Optional user facilities can only be applied to SVCs. Table B-4.
X25AM Parameters Table B-4. X25AM Optional User Facilities (Page 2 of 2) Network Subscription Parameter Possible Values Default Values SCF Attribute SYSGEN Modifier Transit Delay Selection and Indication RPOA Selection 0:00 – 1:05.03 None TRANSITDELAY — Specified as a line attribute in SCF. 0 –9999 None RPOA — CUD Field 1 –16 bytes For PTP SU, the default value is no bytes of user data. For ITI SU, the default value is 4 bytes of zeroes.
Appendix C Utilities for Managing X25AM The X25AM subsystem supports a variety of management and information utilities that can be used to manage, troubleshoot, and maintain X25AM processes, lines, and subdevices.
Utilities for Managing X25AM can receive events from non-Tandem devices. Viewpoint is described in the Viewpoint Manual. Event Management Service (EMS) EMS is a standard DSM interface that provides event collection, logging, and distribution facilities. The X25AM subsystem reports events to EMS. Filters can be written to select the reporting of critical events, and to prevent unwanted messages from propagating across the network.
Utilities for Managing X25AM Tandem Maintenance TMDS is a diagnostic and monitoring utility that can be used to monitor the and Diagnostic controllers supporting X25AM. TMDS is described in detail in the Tandem Maintenance Subsystem (TMDS) and Diagnostic Subsystem (TMDS) Reference Manual Measure Measure is a tool for monitoring the performance of Tandem systems. Measure can be used to determine if the X25AM lines are contributing to performance problems. Measure is described in the Measure User’s Guide.
Appendix D D-Series Changes to X25AM The D-series changes to X25AM are summarized below: The maximum number of subdevices supported per X25AM line has been increased from 254 to 511. The 6202 byte-synchronous controller is no longer supported. CMI is no longer supported. CUP is no longer supported. Generally, applications written for C-series systems should run on D-series systems without being changed in any way.
Glossary This glossary includes a selection of terms used in this manual. Definitions of communications terms are brief and not very detailed. Many textbooks and technical dictionaries define these terms in more detail. 3650/6100 Communications Family. The 3650/6100 Communications Family are programmable controllers, providing multiple protocol support. The product numbers of the 3650/6100 family controllers supported by X25AM are the 3650 CSS (6110), the 6100 CSS (6101), the 6105, and the 3605. ABM.
Glossary call accepted packet. Packet that a remote entity sends to the network in response to an incoming call packet, if a circuit can be established. call clearing. Descriptive phrase for the activities required for disconnecting a switched virtual circuit. call connected packet. Packet that the network sends to a caller in response to receiving a call accepted packet from a remote entity. call redirection. Optional network facility allowing the network to pass a call to another subscriber number.
Glossary CLIP. Communications line interface processor. The CLIP is the part of the line interface unit (LIU) in the 3650/6100 family controllers. Code can be downloaded to the CLIP to provide a link-level protocol. CMI. Communications Management Interface. A subsystem used for issuing configuration and information requests between the user and some communications subsystems. CMI is not supported for D-series X25AM. Also, it does not support all features of X25AM for C-series systems. combined station.
Glossary data packet. Packet containing data. DCE. Data circuit-terminating equipment. In the context of the X.25 standard, the network is identified as a DCE. X25AM can be configured as either DCE or DTE. The term DCE is also used to refer to a modem. destination address. See called address. device. Physical or logical system component. For X25AM, a line is a device defined in the CONFTEXT file. DISC. Disconnect. Link-level frame, used for call disconnection. DNIC. Data Network Identification Code.
Glossary Guardian 90 operating system. Operating system that runs on a Tandem NonStop system. half duplex. Method of serial communications in which the data flow between two points can occur in only one direction at a time. HDLC. High Layer Data Link Control. A protocol specified by the International Organization for Standardization (ISO) for bit-synchronous communications. I-frame. Information frame. Link-level frame containing a packet. incoming call packet.
Glossary LIU. Line Interface Unit. A components of the 3650/6100 Communications Family. Each LIU supports a single communications line. The 3650 CSS and 6100 CSS can have 1 through 15 LIUs. The 3605 and 6105 controllers can have 4 LIUs. logical channel (LCN). Provides the logical connection between the user DTE and the packet exchange. logical channel number. Number assigned to a logical channel to uniquely identify it. logical device. Device that can be accessed and addressed.
Glossary NET/MASTER. One of the DSM products for network management. NET/MASTER provides a common interface for managing both Tandem NonStop systems and IBM systems. network. Group of nodes connected by communications lines. node. Point of connection in a network. Usually consists of a computer or other peripheral device that provides a switching or terminating point in the network. nonswitched line. Line configuration that provides a permanent path between two stations.
Glossary physical level. X.25 protocol description for the physical link between the network and the computers, terminals, or other devices. physical unit (PU). An entity in an SNA network, responsible for the physical configuration of a node. Often identified with the node itself: for instance, a host is a PU type 5. point-to-point. A data link configuration between only two stations. The X.25 standard supports only point-to-point communications.
Glossary RNR. Receiver not ready. Link-level frame or packet-level packet. As a packet, it acknowledges the receipt of data and requests that packet transmission be halted. RPOA. Registered private operating agency. The RPOA is a packet network, value-added carrier, which acts as a transmit network within one country or between countries. RR. Receiver ready. Link-level frame or packet-level packet. As a packet, it acknowledges the receipt of data and requests that packet transmission continue. RS-232-C.
Glossary SUT. Site update tape. Sent from Tandem to a customer, containing a particular release of operating system software and customer-specific software that runs with the operating system. switched line. Line configuration for circuit-switched networks such as a public telephone network. The physical configuration may vary for each usage as a message is routed through switching stations. switched virtual circuit (SVC). A temporary end-to-end connection between two DTEs through a network.
Glossary X.25. Set of international recommendations for the connection between computers, terminals, or other devices and a public or private packet-switching network. X.28. Standard related to X.25. Defines how an asynchronous device communicates with a PAD in the same country. X.29. Standard related to X.25. Defines how an X25 DTE controls the operation of a PAD during communications with an asynchronous DTE. X.75. Standard related to X.25.
Index A Access One 2-18 Address field 1-26 Addresses link-level 1-24 Addressing 1-10 implementation example 3-6 Asynchronous terminals ITI 2-15 local 2-13 remote 2-15 ATP6100 2-14 Attributes SCF B-1/6 B BCUG 2-7 Bilateral closed user group 2-7 Byte-synchronous controller 2-34 C Call line address modified notification 2-9 Call redirection 2-9 Call setup packets 1-17 Call user data 1-17 compared to fast select 2-11 compared to user data 2-11 specification and retrieval 2-11 Card X.
Index Connectivity Tandem systems 2-20 TCP/IP 2-30 to Integrity S2 2-30 to LANs 2-30 to OSI 2-32 to other hosts 2-19 to remote IBM intelligent terminals 2-26 to SNA networks 2-23 types of 2-12 Control field 1-26 Controllers byte-synchronous D-1 supported by X25AM 2-34 WAN and LAN 2-30 Cooperative processing 3-13 CUG See Closed user group CUP D-1 D D bit 1-16 D-series changes D-1 Data call user 1-17 user 1-17 Data transfer I-frames 1-29 link-level 1-29 packet-level 1-21 Data-Link Layer 1-24 DCE 1-3 Defaults
Index DTE 1-3 Dynamic System Configuration features of C-2 E Eicon card 2-19 implementation example 3-8 Electrical interfaces 1-35 Electronic-mail messaging 3-1 EM3270 2-24 EMS See Event Management Service Event Management Service features of C-2 Expand 1-1, 2-20 F Facilities optional user 2-5 Fast-select 2-6 product number 5701-X25EE restrictions 2-6 FCC 1-2 FCS field 1-27 Fields 1-26 Flag 1-26 Format packet 1-15 Frame structure 1-26 types 1-31 DISC 1-33 DM 1-33 FRMR 1-33, 1-35 I-frames 1-31 REJ frames 1-
Index frame-relay network interfacing X25AM with 3-14 Framing process 1-24 FRMR diagnostic field 1-35 G Gateways 1-9 General format identifier 1-16 GFI See General format identifier H HDLC 1-11 I Information field 1-27 InfoWay 2-22 Integrating Guardian NonStop Systems with the Integrity S2 3-2 Integrity S2 2-10, 3-2 ITI 2-15 implementation example 3-10 L LAN Access One 2-18 UB gateway 2-18 LAP 1-11, 1-24 LAPB 1-11, 1-24 Layer data-link 1-12, 1-24 packet 1-12 physical 1-35 LCGN See Logical channel group num
Index Line X25AM 2-2 Link protocol B-1 Load-sharing implementation example 3-6 Logical channel 1-14/15 group number 1-16 number 1-16 M M bit 1-17 Management utilities C-1/3 Measure features of C-3 MFC 2-34 Microwave 3-10 Modifiers SYSGEN B-1/6 Modulo frame-layer 1-30 packet-layer 1-21 N NAM 2-20 Negotiation packet size 2-8 throughput class 2-8 window size 2-8 NET 2-20 NET/MASTER features of C-2 NETID 2-11 Network defaults 2-11 Network subscription parameters supported by X25AM B-1/6 065307 Tandem Computer
Index Networking conventions IBM 1-1 proprietary 1-1 SNA 1-1 Tandem 1-1 X.
Index Packet types 1-19/23 call clear clear request and clear indication 1-20 call setup call accepted and call connected 1-19 call request and incoming call 1-19 data 1-21 diagnostic 1-23 flow control RR and RNR 1-23 interrupt 1-23 reset 1-23 restart 1-23 Packet-switching data network 1-1, 1-3 supported by X25AM A-1 PAD 1-6 parameters 2-14, 2-15 standards relating to 1-6 without a packet-switching data network 2-17 Parameters supported by X25AM B-1/6 Peripheral Utility Program features of C-2 permanent vi
Index Q Q bit 1-16 QLLC 2-23 R RDF 3-4 REMOTENET 2-11 Restrictions product number 5701-X25EE 2-6 Reverse-charging 2-7 Routing 1-13 RPOA selection 2-10 RS-232C 1-36 RS-449 1-36 S SCF 2-2 See Subsystem Control Facility Sequencing numbers frame-layer 1-30 packet-layer 1-21 SNA 1-4, 2-23 SNAX/CM 2-25/29 multiple processes 2-29 SNAX/XF over X25AM 2-23 implementation examples 3-4, 3-8 SPI See Subsystem Programmatic Interface Standards internetwork 1-9 ISO 1-9 X.
Index Subaddressing 1-10, 2-4 implementation example 3-6 Subdevices 2-2 C-series 2-2 CIRCUITS modifier 2-2 configuration 2-2 D-series 2-2 maximum number D-1 Subsystem Control Facility features of C-1 Subsystem Programmatic Interface features of C-1 Support X25AM 2-1 SVC See Switched virtual circuit Switched virtual circuit 1-13 call setup and call clearing packets 1-13 SysWay 2-22 T Tandem Maintenance and Diagnostic Subsystem features of C-2 TCP/IP 2-30 TCP/IP over X25AM implementation example 3-12 Through
Index V V.35 1-36 V.36 1-36 Values B-1/6 Viewpoint features of C-1 Virtual circuit See Switched virtual circuit W Window rotation packet-layer 1-21 Window size frame-layer 1-30 negotiation 2-8 packet-layer 1-21 X X.121 addresses 1-10 implementation example 3-6 X.21 1-36 X.21 bis 1-35 X.25 benefits 1-1 card 2-19 comparison with other networking standards 1-4 layers 1-11 recommendation 1-2 history 1-2 Tandem 2-1 using with direction connections 1-5 X.28 1-8 X.29 1-8, 2-14 X.3 1-6, 2-14 X.
Index X25AM comparing to OSI model 2-1 components 2-1 connectivity 2-12 controllers 2-34 DCE or DTE 2-1 LAP 2-1 LAPB 2-1 line 2-2 process 2-1 protocols 2-12 scope of support 2-1 subdevice 2-2 X3PAD 2-13/14 065307 Tandem Computers Incorporated Index–11
